1,000,000 Question Thread :D

[kenhung123]

Is it?

[kenhung123]

How many components have been used to make colour A?

Is it 3?

[Aden]

Yes, you are correct for all three questions. There are usually given answers at the back of the textbook, and this section definitely exists in the Heinemann version (which is the one I think you're using).

[kenhung123]

THe answers say something else.

[kenhung123]

A sample of whisky is being determined for its % v/v ethanol concentration. 20mL of the whisky is first diluted to 200mL. The diluted solution is then passed through the GCL and its peak area is found to be 250 arbitary units.

[enwiabe]

I have not touched this type of Chemistry in 3 years, but here's my best effort

From the graph, we see that the diluted solution's 250 arbitrary units of peak area corresponds to roughly 5% v/v ethanol.

But that's of the DILUTED solution. We now have to work out the dilution factor of the solution being tested.

Remember that they took 20 mL of whiskey and added 180 mL of water.

Remembering that , the amount of whiskey in the sample will not change, and only its concentration from undiluted to diluted will. Applying this principle of conservation of mass (amount of stuff), we see that



We know that (converted 20 mL = 0.02L), and we know that

Thus, plugging this in,



and so,



Which means that the dilution factor is 10. This makes sense that if you dilute a sample from 20 mL to 200mL (increase volume by 10 times), then the concentration decreases by a factor of 10.

So as we worked out from the graph,

therefore,

% v/v

If I got this wrong I am going to cry and just stick to the maths boards

[kenhung123]

You got it right!

Thanks man!